Electric amplifying system



Nov. 18, 1941.

H. BOUCKE ELECTRIC AMPLIFYING SYSTEM 3 sheets-sheet 1 Filed April 26,1959 FIG-6 FIG-5 INVENTOR,

HEI N z Bouc KE FIG? ATTORNEY.

Nov.; 18, 1941. K H. BoUcKF.

ELECTRIC MPLIFYING SYSTEM Filed April 26, 1959 3 Sheets-Sheet 2AAAAlAAAL .R ma Nm E WU 1o a z m E .H

ATTORNEY.

Nov. 18, 1941. H. BoUcKE 2,262,915

ELECTRIC AMPLIFYING' SYSTEM Filed April 26, 1939 3 Sheets-Sheet 3INVENTOR.

ATTORNEY.

AAAAAA HEINZ BOLJCKE I l L.,

#Awww n :nx

Patented Nov. 18, 1941 2,262,916 ELECTRIC AMPLIFYING SYSTEM HeinzBoucke, Berlin-Charlottenburg, Germany,

assignor to Radio Patents Corporation, a corporation of New York iApplication April 26, 1939, Serial No. 270,053 In Germany May 30, 193816 Claims.

Thelpresent invention relates to electron valve' amplifiers and a methodof operating the same, more particularly to aperiodic or direct coupledmulti-stage amplifiers for translating or amplifying signals comprisinga substantial frequency band or for amplifying relatively slow periodicor aperiodic variations of electric current or potential. There arenumerous applications for amplifiers of this type such as in industrialcontrol equipment, telegraphic signalling, measuring systems, in radioreceivers and various other uses.

An object of the invention is the provision of a direct coupled electronvalve amplifier comprising two or more amplifying stages embodied in asingle amplifying Valve.

Another object is the provision of a novel automatic volume control (A.V. C.) arrangement for use in radio receivers or the like characteriZedby substantially increased sensitivity and efficiency compared with A.V. C, systems at present known in the art.

A more specific object is to provide a self-regulating amplifier orvolume limiting device adapted to automatically maintain a desiredoutput level in a radio receiverr or any other amplifying system.

' Another object is to provide a multi-grid electron valve amplifiercapable of simultaneously amplifying both direct and alternatingcurrents.

`With the above objects in view, the invention contemplates lthe use ofa multi-grid electron valve amplifier having an input contro1 grid uponwhich are impressed the potential variations to be amplified to causecorresponding fluctuations of the electron stream passing through thevalve. Amplified potential variations are derived from the firstpositive or anode grid `and impressed through a direct current couplingarrangement upon a second control grid arranged to control the sameelectron stream. Suitable compensating means are provided to suppressthe effect of the positive operating potential at the anode grid uponthe second control grid and to maintain the latter at a suitablepreferably negatively biased operating point to ensure efficient andfaithful amplification and Itranslation of the input potentialvariations within a desired operating range. Further direct coupledstages may be included in the same valve for additionally controllingthe common electron stream. The final amplified potential or current isderived from an anode and/or one of the positive grid electrodes.

The above and further objects and aspects of the invention will becomemore apparent from 55 the potentiometer resistancey 2'0.

vthe applied input potential.

the following detailed description taken .with refei'ence to theaccompanying drawings illustrating several practical embodiments of theinvention and wherein:

Figures 1 to 7 representsimple direct coupled two-stage amplifiercircuits embodying a multigrid electron valve in accordance with theinvention,

l Figures 8 and `9 illustrate circuits yembodying a multi-grid valveproviding more than two amplifying stages,

Figure 10 lillustrates an lamplifier stage of a radio receiver or thelike embodying the improvements of the invention for automaticallycontrolling the output volume oi 'the receiver,

Figure 11 shows an amplier stage in a radio receiver 'or the likeembodying the improvements of the invention for suppressinginter-carrier noises during the tuning of the receiver,

Figures 12 and 13 are graphs illustrative of the function'and novel.effect `obtained by the invention,

Figure 14 .illustrates the invention as embodied in a radio receiver forobtaining improved automaticvolume control.

Similar reference numerals identify similar parts ythroughout thedifferent views' of the drawings.

yReferring to the drawings, Figure 1 shows a simple direct coupledamplifier constructed -in` accordance with the invention and comprisinga multi-grid valve Ihaving a cathode I-I which may be of either thedirectly or indirectly heated type, aninput control grid I2, a first'positively biased or anode grid I3, in theexample shown' having the formof a space Vcharge grid located nearv the vcatl'iode,` a secondpreferably negatively biased control` grid` I4 and an anode I5. Theinput voltage to be amplified is impressed between the cathode I I andinput grid I2 through terminals a, b the latter being shunted byl aninput impedance such as an ohmic resistance I8. The positive or anodegrid I3 is connected to the positive vterminal of a high tension supplysource 'represented by the potentiometer resistance I9 through ai loadimpedance 2| whereby amplified potential variations will be developed atthe grid I3 corresponding to the variations of- These potentialvariations are'impressed directly and conductively upon the control gridI'lI through a potential divider resistance 22 connected between thegrid I3 and the negative terminal `of a compensating battery orpotential source represented by The positive tive operating point toensure most favorable' operating conditions and efficient amplification'of the electron current variations. The ampli.-

iied current variations may serve'fftd operate a" measuring instrument23 if the system serves for measuring purposes, or alternatively, theinstru# ment 23 may bereplaced by ay suitable Acoupling impedance ornetwork -for applying theHampli-` ed current or potential variations toa suitable translating device or to a further amplifying f In-theaforeldescribed 'arrangement the electron discharge current passingthrough the valve from the cathode to the yanode is subjected to thesimultaneous..control'y by the 'two gridsV I3 and..|4 f i. 11. l. I

:Figure 2 showsa two-stage direct coupled am` plifler similar to Figure1 wherein a special vcom-l pensatingsource is dispensedwithVA by theprovision of a resistance 25 in series with'the-cathode lead or groundof the valve. Theeffectof vthis resistance is to render the. controlgrid I4 negative relative to .the cathode thereby. c'ompensat`ingtheefect ofthe positive or vanode potentialk asa. result oftheconductive connectionv bet-Ween the. :grids I3 and I4.. This kind .ofcompensation shown in the embodiment Figure 5 being otherwise similar toFigure 4. Alternatively; the screen grid may be omitted or separatescreens arranged at opposite sides of the positive or anode grid I3. Inan arrangement of this type the grids I2 and I4 are controlled inanti-phase relation 'due to the fact that a phase reversal takes placebetween the first and second control in a manner' similar to that of anordinary triode amplifier. Since, however, the second 'control potentialon the grid I4 is substantially amplied, the control bythe seco-nd gridmay be vcaused,tovpredominate over the control by the `-zfffirst grid byproperldesign of the circuit elements,

'resulting .in a considerable increase of amplifica- Vtion." In thearrangements according to Figures 1 .31 on the other hand, the grids I2and I4 are ofthe steady positive potential'is possible due i totheifactthat the total anode current passing currents flowing to thepositive grid 'I3 and to;

thejanodeis efectedby. asyarying' relative distributionv ofKV th'etotaldischarge y currentV `in ac. cordance with the applied controlpotential.;4 I.

t, In the circuit arrangement Y according td, Figures l and 2, a directcurrent feedbackexists Adue, to the fact that the potentialvariationsjofthe, secondY control grid v I4 react `upon ,f theY yspacecharge or anode grid |53. This reaction is yminis; mized :according toFiguI-efby theprovision of. a screen grid 2,6 arrangedbetweentheinputigl'id3- I2 -zand the second controljgrid I4 and connected toagrsuit'able positive pointr of the highgpotentialj source such asa, tappoint of the potentiometer resistance .I3 as shown. .By controlling thelpotential of the screen grid 26 such Aas byvarying1 the-voltage drop orbleeder resistance 26( placed inthe screen: gridlead itis possible to,adjustL the, direct f current reaction requirements. Y h y h Accordingto a modiiication van increased con- 4to suit any existing.

trollingv action ofthe inputgridis obtained byv employing an input gridlocated near the cathode;

' and by deriving amplied potential from -a posi tively biased oranodegrid spaced therefrom in; thev direction of the anode. p. A circuitarrange-- ment of this type is'shown in Figure 4. In the:

latter the input grid I2 islocated near the cath-l ode andrtl'ievpositive grid I3 placed nexttothe,Y

second control gridv I4. The screen grid in thisl modication is arrangedlbetween thek inputv grid; I2 and-the positive ,grid- I3. Alternatively,the screenl grid may be. placed betweenI the ,positivej grid'-13C-andthe second control K grid |247 such as; 75

.excited in' like phase since the current to the in Figure 4 in view ofthe location of grid I3 on the, opposite side of the input grid I2.

. In a circuit according'to Figure 5 wherein-the.

screen grid 2 6-is placed between'the positive grid I 3 and the secondcontrolgrid I4, the direct Acurrent reaction between these grids issubstantially reduced. If nevertheless in an arrangement of this type acertainv amount of reaction is desired a separate exterior feedbackcircuit may be provided lj such vas shown in Figure 6. In the latter,the anode I5 is directly connected to the input. grid I2 through aresistance 29. r'I'he effect of the anodepotential on the input grid i-scom` pensatedbya suitable counter potential derived' in the exampleshown l from thel potentiometery resistance 2l) which also` serves forcompensating@ thepositive potential 'on the second control grid I4.order to adjust the compensating potential, there is provided a voltagedivider 30 connected between the input 'grid' I2 and the negativeterminal of the. compensating potential to the grid I2 on the one handand to a variable tap point of the potential divider 30. In order todevelop feedback potentials at the anode/'I5 5 therei's provided a-suitableload resistance28 in inverting "valveis used .between theoutputof thep'ositive grid I3 and thefsecond control grid pressed uponthe second control grid I4 yof the. amplifier I0 being of similar designto that in the preceding embodiments. v`For this purpose y the anode ofthe valve.32 is further connected .to4

source,v the input impedance VI3 being connected In this case,- itwouldnot suiice'to' provide one or more screen grids to eliminate'reactionand according to a' further rfeature of 'the invention al special phasevA circuit -arr'angement :of this type is shown in Figure 7. Inthelatter, the amplified poten-Y the negative pole of the compensatingpotential source 20 through a potentiometer resistance 31 and a variabletap of the latter is connected to the second control grid I4 of valveI0. By this connection, the effect of the high potential on the anode 35of valve 32 upon the grid I4 of valve I is compensated in a mannerreadily understood from the above.

According to a further modification, the number of amplifying stages maybe increased or the electron discharge current controlled at more thantwo points by the same potential such as shown in the exemplicationsaccording to Figures 8 and 9. In Figure 8, the cathode II, input gridI2, positive grid I3 and second control grid together with loadresistance 2l and compensating potentiometer 22 constitute a two-stagedirect coupled amplifier substantially similar as shown in Figures l and3. In order to obtain additional amplification in the same valve, thereis provided a further positive grid I3 having connected thereto a loadresistance 2I and compensating resistance 22 in a manner substantiallysimilar as the iirst positive grid I3. The compensating resistance 22has a variable tap connected to a further control grid I4. Any desirednumber of additional amplifying stages may loe provided in this manneras will be readily understood. In the example illustrated a fourstageamplifier is shown, the corresponding elements of the separate stagesbeing identified by similar but primed reference numerals as used forthe first two amplifying stages.

Referring to Figure 9, there is shown a multistage amplifier similar tothe preceding embodiment wherein the grid electrodes for the severalamplifying stages are arranged relatively as shown in Figures 4 and 5.In the latter arrangement, a phase reversal by 180 takes place betweensuccessive amplifying stages while in case of Figure 8 all the controlsof the common electron stream by the grids I2, I4, Id', I4, etc., act inthe same sense as will be readily understood from the above. Thefunction of the screen grids and other elements is substantially similaras described in connection with the two-stage amplifier shown in thepreceding diagrams.

The arrangements described hereinbefore are specially suited for theamplification of variable direct potentials or currents. Thus, theamplifiers may be used in the measuring art or for amplifying controlpotentials such as AVCv (automatic volume control), AFC (automaticfrequency control) potentials, volume expanding potentials inradio'receivers or the like. In many cases an existing multi-grid valvefor low frequency or high frequency amplification may be usedadditionally as a multi-stage direct coupled amplier for amplifying apotential serving to control the operation of the amplifier. In thismanner it is possible to `effect substantial variations of thealternating current amplification with a comparatively weak controlpotential with a minimum of Valves and circuit elements.

In Figure l2 there is shown a graph illustrating the variation of theanode current in an amplifier of the aforedescribed type Ain dependenceupon the direct potential applied to the input of the valve such as in acircuit of the type according to Figures l, 2 and 3. As is seen, avariation of the direct grid potential by about .5 volt is sufcient tochange the amplification from Zero to its maximum value. Theamplification of an alternating potential which may be additionallyapplied to the input grid is determined bythe known operatingcharacteristic of the valve. The auxiliary grids I3 and I4 in this caseemployed for the additional direct current amplification should beby-passed or grounded forthe alternating potential by means ofcondensers.`

If in the arrangements according to Figures 1 to 8 suitable alternatingcurrent circuits are connected to the input grid and to the anode suchas is customary in low frequency or high frequency amplifiers, and if adirect control potential is simultaneously impressed upon the input gridthere is obtained in this manner a low frequency or high frequencyamplifying stage particularly well adapted for automatic volume controland/or volume expansion. The degree of the direct current amplificationmay be varied by suitably adjusting the values of the resistances 2| and22 between substantial limits.

The high sensitivity of the adjustment of the amplication by smallvariations of direct potential makes it possible further to obtain .anautomatic volume control without requiring `an additional AVC or outsidecontrol potential or in other words to provide a self-regulating orlimiting amplier. For this purpose it is only necessary to adjust theoperating point upon the curved part of the characteristic for the inputgrid I2 in such a manner as to cause a partial rectification of theapplied alternating potential resulting in direct potential variationson the positive grid electrode I3. These potential variations, dependingon the location of the electrode, may serve to effect an amplitudelimitationor increase of the alternating potentials derived from theanode.

An exemplication of a circuit of this type is shown in Figure Il0. Inthe latter, if the valve used has a curved mutual characteristicrepresenting current in the circuit of the positive grid I3 as afunction of the potential on the grid I2, a partial rectification of thealternating potential impressed across the transformer 40 will takeplace resulting in corresponding variation of the steady potential onthe grid I3. As the amplitude of the impressed alternating potentialincreases, the direct potential on the grid I3 becomes less positive insuch a manner that the amplied direct potential on the grid I4 willbecome more negative. resulting in a decrease of the electron dischargecurrent flowing to the anode I5. In this manner, the amplifiedalternating output current translated through the tuned transformer 42to the output terminals c, d is automatically maintained at apredetermined level in a manner similar to the operation of knownautomatic volume control systems but Without requiring a separateexternal -control potential produced b-y a separate rectifier in amanner well known. The partial rectieation of the input alternatingpotential may also be effected in a different way such as byrectification in the grid circuit or in any other suitable manner. In anarrangement of this type the control potential applied from the grid I3to the grid I4 should be sufficiently ltered such as by the provision ofground by-pass condensers 44 and il if the control is to be dependentupon the average amplitude of the alternating potential rather than uponits fluctuations or modulation. Condensers 45 and 46 are the usualgrounding or by-pass condensers for the screen grid 26 and the hightension supply source, respectively.

The fact that by an arrangement according to the invention, provided theresistances 2| and 22 vare properly designed, it is possible 'to securea sudden increase in amplification by means of a small variation of acontrol potential while with further increase of the control potentialin the same sense the amplification is only slightly afis blocked forsmall control potentials and suddenly assumes its full amplification ata determined potential which may be adjusted to suit any existingrequirements. An example of an arrangement of this type is illustratedin Figure 11. In the latter, the `low frequency potential to beamplified is applied through coupling condenser 48 to the input gridI2and the amplified output potential derived by means of couplingcondenser 52 and coupling resistance 53 in a manner well understood. Theoutput potential may be applied to a succeeding stage of amplificationor to a suitable translating device. The direct current amplifier is ofthe type to effect a phase reversal between successive amplifying stageswhereby with the AVC potential Er impressed to normally render the gridI2 negative as shown in the drawings, the tube will be blocked for smallvalues of the negative grid potential and become conductive .withincreasing control potential. If the control potential is furtherincreased, the amplication again begins to decrease provided a valve isused having a regulating or variable mu characteristic for the first orinput grid. This decrease in amplification enables an efficient volumecontrol by reason of the fact that the decreaseis inversely proportionalto the output potential of the preceding high frequency amplifier; InFigure 13 is shown a graph further explaining the operation of Figure 1lrepresenting anode current as a function of input grid potential in atwo-stage direct coupled amplier of the type provided in Figure 11 andgenerally illustrated in Figures 4, 5, 6. This graph differs from Figurel2 corresponding to circuits of the type of Figures 1-3 by a reversal ofthe output phase as explained herein#- before.

It is evident from the above that the arrangements according to theinvention are susceptible of numerous modifications and variationscoming within the broader scope and spirit of the invention. Thus, it ispossible to provide further grids or auxiliary anodes within a valveserving to produce additional effects or to construct the electrodes inany desired form. Furthermore, the circuits shown may be embodied in areex amplifier using the same valve for radio, audio and direct currentamplification. When simultaneously using a valve for amplification of adirect potential and alternating potential as described herein, it isalso possible to apply the input potential to separate grids; that is,to apply the alternating potential to one grid and the direct potentialto another input grid. It is also possible to derive the amplifiedalternating potential from one of the positive grids I3, I3', I3", etc.,instead of from the anode circuit or simultaneously from bo-th or one ormore of the positive grids. In the latter case the positive grid usedfor deriving alternating potential should not be by-passed or groundedfor the potentials to be derived and in addition a suitable filtershould `be provided to prevent the alternating potential from beingimpressed upon the succeeding control grid. The arrangements describedfor direct current amplification, especially those embodying positivereaction are also suited for generation of oscillations, both sinusoidaloscillations by the provision of suitable capacities and self-inductioncoils and for the generation of relaxation oscillations as used intelevision.

In order to avoid in the arrangements shown excessive control swings ofthe grid I3 beyond the negative region and to prevent appreciable gridcurrents, the control potential may be impressed upon this grid througha high ohmic resistance in which case the grid is preferably grounded orby-passed for high or low frequency;

Referring to Figure 14, there is shown a re' ceiving circuit forbroadcast signals embodying an improved automatic volume controlarrangement according to the invention. The signals absorbed by anantenna 55 are impressed through a tuned coupling transformer 56 uponthe grid- -cathode path of a multi-grid amplifying valve I0 of the typedescribed hereinbefore. The amplied high frequency signals aresegregated by means of a tuned transformer 58 in the anode circuit ofthe valve and impressed upon a pair of diode rectifiers Ill and 'II inparallel through coupling condensers I2 and i3, respectively. The

output of the rectifier II is fed through a network comprising asmoothing resistance 18, smoothing condenser and volume. control po-`tentiometer I9 to an audio amplifier 8| having 4its output connected toa suitable translating device such as a loud speaker 82. The rectifier'Ill serves to produce AVC potential applied through resistancesv'M and'I5 to the grid I2 of the valve Ill in such a manner as to normallymaintain the grid positive relative to the cathode. This AVC potentialwhich may be of relatively small value compared with AVC potentials re`quired in the known AVC arrangement in use today is amplified by thetube I0 acting simultaneously as a direct coupled multi-stage ampli@Vfier in accordance with the invention, as described in detailhereinbefore. For this purpose the positive grid I3 is connected to asuitable tap point of the potentiometer resistance 64 while the secondcontrol grid I4 is connected to a tap point of a further potentiometerresistance 65 in series with the first resistance 64 and connected tothe positive pole of the high potential or anode current supply sourceon the one hand and the negative potential or ground on the other hand.Item 59 represents a compensating resistance in the cathode leadby-passed for highv frequency by a condenser 6I and serving to eliminatethe effect of the high potential on the control grid I4. Both thepositive grid I3 and the second control grid I4 are by-passed to groundfor high frequency by by-pass condensers 56 and 61, respectively.

In the afore-described arrangement, variations of the AVC potential Ersupplied by the rectifier 10 will cause similar variations of thepotentials on the grids I3 and I4 in such a manner that by a slightdecrease of the negative bias of the input grid I2 (slight increase ofthe AVC' potential), the negative potential of the grid I4 increases tosuch an extent as to substantially decrease the anode current due to thecurrent distribution control. By suitable design of the circuit elementsand operating potentials it is possible to effect a change of the degreeof amplification between a minimum and maximum by varying the controlpotential Er from .5 to- 1.5 volts.

As will be evident from the foregoing the novel circuit according to theinvention is susceptible of various other modifications and applicationscoming within the broad scope and spirit of the invention as dened inthe appended claims. The specification and drawings are accordingly tobe regarded in an illustrative rather than a limiting sense. Thus, thecathode heating and plate potential supply sources, by-pass condensersor choke coils to prevent direct or alternating currents from enteringcertain circuit portions but to enable them to readily pass throughother circuits of the system, and other conventional elements anddetails have not been shown as being immaterial to the understanding ofthe invention and for clarity of disclosure and simplification of thedrawings.

I claim:

1. In a combined alternating. current-direct current amplifier, anelectron valve having a cathode, an anode and a plurality of gridslocated at different points in the electron stream passing from saidcathode to said anode, alternating current input and output circuitsoperatively connected to an input grid and to said anode, respectively,for amplifying an alternating current signal, further means forimpressing direct potential variations upon a rst grid of said valve,means comprising a load resistance and a source of positive potentialconnected to a second grid to produce amplied direct potentialvariations at said second grid, a conductive coupling connection fromsaid second grid to a third grid of said valve, means to compensate theeffect upon said third grid of the positive potential at said secondgrid, and further means to prevent alternating potential from affectingsaid third grid. i

2. In a combined alternating current-direct current amplier, an electronvalve having a cathode, an anode and a plurality of grids located atdifferent points in the electron stream passing from said cathode tosaid anode, alternating current input and output circuits connected to afirst grid and to said anode, respectively, for amplifying analternating current signal, further means for impressing directpotential variations upon said rst grid, means comprising a loadresistance and a source of positive potential connected to a second gridto produce amplified direct. potentials at said second grid, aconductive coupling connection from said second grid to a third gridadapted to control the operation of said valve, means to compensate theeifect upon said third grid of the positive potential at'said secondgrid, and further means for preventing alteranting potential fromaffecting said third grid.

3. In a combined alternating current-direct current amplifier, anelectron valve having a cathode, an anode and a plurality of gridslocated at -dilerent points in the electron stream passing from saidcathode to said anode, alternating current input and output circuitsconnected to a first grid and to said anode, respectively, foramplifying an alternating current signal, means for producing a directpotential varying according to the average amplitude of the alternatingcurrent beingamplified, means for impressing said direct potential uponsaid first grid, further means comprising a load resistance and a sourceof positive potential connected to a second grid to produce amplieddirect potential at said second grid, a conductive coupling connectionfrom said second compensating the eie'ct upon said third g'rid'of thepositive potential at said second grid,va`nd means to preventalternating potential from affecing said third grid. l

4. In a combined alternating current-direct current ampliiier, anelectron valve comprising a cathode, an anode, a rst grid located nearsaid cathode, alternating current input and output circuits connected tosaid grid and anode, respectively, `for amplifying an alternatingcurrent signal, means for producing a direct potential `varying inaccordance with the average amplitude of the alternating current beingampliedpmeans for impressing said direct potential upon said rst grid innegative polarity relation to said cathode, further means comprising aload resistance and a source of positive potential connected to a secondgrid spaced from said rst gridin adirection towards the anode to produceamplied direct potential variations at said second grid, a conductivecoupling connection from said second grid to a third grid adapted tocontrol the amplifying gain of said valve, means to compensate the`effect upon said third grid of the positive.V

potential at said second grid, and means to prevent alternatingpotential from aifecting said. second and third grid.

5. In a combined alternating current-direct current ampliiier, anelectron valve having ya cathode and an anode, a rst grid located nearIsaid cathode, input and output circuits connected to said grid and saidanode, respectively, for amplifying a modulated carrier signal by saidvalve, means for producing a direct control potential varying inaccordance with the carrier amplitude of said signal, means forimpressing said control potential upon saidl grid in positive polarityrelation to said cathode, further means comprising a load resistance anda source of positive potential connected-to a second grid spaced fromsaid rst grid in a direction towards said anode to produce amplifieddirect potential at said second grid, a conductive coupling connectionfrom said second grid to a third grid near said anode adapted to controlthe amplifying gain of said valve, means to compensate the effect uponsaid third grid of the positive potential upon said second grid, andmeans to prevent carrier potential from' affecting said second and thirdgrids. Y

. 6. In a combined alternating current-direct current amplifier, .anelectron valve having ka l cathode and an anode, a rst grid located nearsaid cathode, input and output circuits connected to said grid and saidanode, respectively, for amplifying a modulated carrier signal by saidvalve, means for producing a direct control potential varying inaccordance with the carrieramplitude of said signal, Ameans forimpressing said control potential upon said first grid in positivepolarity relation to said cathode, further means comprising a loadresistance and a source of positive potential connected to a second gridspaced from said rst grid in a direction toward said anode to produceamplified direct potential at said second grid, a conductive coupling'connection from .said second grid to a Athird grid, means forcompensating the effect upon said third grid by the positive potentialat said second grid, and means to prevent carrier potential froaffecting said second and third grids. '7. A self-regulating amplifyingstage comprising an electron valve having a cathode, an anode and aplurality of grids located at diierent' points in the electron steampassing from said cathodeA source of positive potential connected to avsecond grid spaced'from said first grid in a direction towards theanode, the mutual operating characteristic for said second `grid inrelation to said first grid being such as to produce a rectifiednegative potential at said second grid varying ,in proportion to thevaverage amplitude of the alternating potential to be amplified impressedupon said iirst grid, a direct current coupling connection from saidsecond grid to a third grid spaced therefrom in a direction towards rtheanode and adapted to control the amplifying gain of saidrvalve, means tocompensate the elect upon said third grid of the positive potential atsaid second grid, and further means to prevent alternating potentialfrom aecting said third grid. l

r8. A self-regulating amplifying stage comprising a multi-grid electronvalve having input and output circuits operatively connected thereto foramplifying oscillatory signal energy, means operatively connected withone of the grid electrodes of said valve other than the input grid forproducing thereon a rectied negative potential varying in proportion tothe average amplitude of the energy to be amplified, a conductivecoupling connection from said last grid to afurther grid electrodeadapted to control the amplifying gain of said valve, andmeans toprevent oscillatory potential from affecting said grid electrodes. l l

9. An electrical system comprising anjelectron discharge tube having acathode, an anode and at least three grids located in the path of theelectron currentv passing from said cathode to said anode, space currentsupply means for` mainrent potentials with respect to said cathode, a

source of signal energy, means for coupling said source to said firstcontrol grid and cathode, load impedance means connected to said anodegrid to develop signal potential variations on said anode grid, meansfor applying the signal potential on said anode grid to said secondcontrol grid, and a signal output circuit connected to said anode andcathode.

12. A direct current amplifier comprising an electron discharge tubehaving a cathode, an anode grid, a first control grid, a second controlgrid and an anode, all arranged in spaced rela tion in the order namedwith respect to said cathode, space current supply means for maintainingsaid anode grid and said anode at positive direct current potentialswith respect to said cathode, means for impressing a varying directcurrent potential between said rst control grid and said cathode, directcurrent load impedance means in the output circuit of said anode grid todevelop potential variations pro,- portional to said impressed potentialon said anode grid, a conductive coupling connection from said anodegrid to said second control grid, means to compensate the effect uponsaid second control grid of the steady potential on said taining a iirstof said grids at a positive potential with respect to thecathode, asource of modulated carrier signals coupled to a second grid and thecathode, a signal output circuit coupled to said anode and said cathode,means including load impedance means connected to said first grid todevelopa potential at said rst grid varying in proportion tofluctuations of the carrier component of said signals, a directconductive coupling connection from said first grid to the thirdrgrid,and means to compensate the eiiect of the positive 'potential of saidfirst grid upon Said third grid.

10. An electrical system comprising an electron discharge tube having acathode, an anode and at least threeA grids located in the path of theelectron current passing from said cathode to said anode, space currentsupply means for maintaining a iirst of said grids at a positivepotential with respectl to the cathode, a source of modulated carriersignals coupled to a second grid and the cathode, a signal outputcircuit coupled to said anode and said cathode, means including loadimpedance means connected to said first grid to developfa potential atsaid iirst grid varying in proportion to fluctuations of the carriercomponent of said signals, a direct conductive coupling connection fromsaid first grid to the third grid,l meansto compensate the effect of thepositive potential of said first grid upon said third grid, and ascreening electrode intervening between said first and third grids.

11. An electrical amplifier comprising an electron-dischargetube`having' a cathode, an anode anode grid, and a signal output circuitconnected to said anode and cathode.

13. A direct current ampliiier comprising an electron discharge tubehaving a cathode, an anode grid, -a first control grid, a second controlgrid and an anode, all arranged in spaced relation in the order namedwith respect to said cathode, a source of space current connected acrosssaid anode and cathode,.a resistive impedance inserted between saidcathode and said source, means for impressing positive bias potentialfrom said source upon said anode grid, means for impressing varyingdirect current potential between said first control grid and a point ofsaid impedance close to said cathode, direct current load impedancemeans connected l to said anode grid to develop potential variationsproportional to said impressed potential on said anode grid, aconductive coupling connection from said anode grid to said secondcontrol grid, and a signal translating device inserted in the anodecircuit of said tube.

14. A direct currnet amplifier comprising an electron discharge tubehaving a cathode, an' anode grid, a rst control grid, a second controlgrid `and an anode, a source of space current connected across/saidanode and cathode, a resistive impedance inserted between said cathodeand said source, means for impressing positive biasing potential fromsaid source upon said anode grid, means for applying varying directcurrent potential between said control grid and a point of saidimpedance close to said cathode, direct current load impedance meansconnected to said anode grid to develop potential variations pro-`portional to said impressed potential on said anode grid, a conductivecoupling connection from said anode grid to said second control grid,

and a signal translating device inserted in the tube having av cathode,anianode and a plurality f of grids located at different points in theelectron stream passing from said cathode to said anode, alternatingcurrent input and output circuits operatively connected to an input gridand said anode, respectively, for amplifying an alternating currentsignal, means for impressing direct current potential variations upon arst grid of said tube, means comprising a load resistance and a sourceof positive potential connected to a second grid to produce amplifieddirect current potential at said second grid, a conductive couplingconnection from said second grid to a third grid of said tube, and meansto compensate the effect upon said third grid of the steady potential onsaid second grid.

16. A direct current amplifier comprising an electron discharge tubehaving a cathode, an anode grid, a first control grid, a second controlgrid and an anode, space current supply means for maintaining said anodegrid and said anode at positive direct current potentials With respectto said cathode, means for impressing a direct current input potentialbetween said first control grid and said cathode, direct current loadimpedance means connected to said anode grid to develop potentialvariations proportional to said impressed potential on said anode grid,a conductive coupling connection from said anode grid to said secondcontrol grid, means to compensate the effect upon said second controlgrid of the steady potential on said anode grid, said control grids andsaid anode grid being relatively arranged so that potential variationson said second control grid are substantially in phase With the inputpotential variations on said first control grid, and a signal outputcircuit connected to said anode and cathode.

HEINZ BOUCKE.

